含水量对对二甲苯氧化主反应过程的影响

Effect of Water Content on Rate of Catalytic Oxidation of p - Xylene

研究了含水量对对二甲苯高温液相氧化主反应的影响规律。实验发现,反应前期的快反应步骤随含水量的增加而单调减缓;反应后期的慢反应步骤则随含水量的增加先加快后减缓,出现一个最大值,此时总氧化时间最短。加入水的两种作用为:改变催化剂配位络合物形式,影响反应传递过程中的电子转移速率常数;降低钴离子氧化还原电势,有利于加快反应。这两种作用竞争导致最佳含水量的存在。

Effect of water content on main reaction steps of p - xylene liquid phase oxidation at high concentration of Br was investigated. For the first two fast steps of p - xylene and toluic aldehyde oxidation, the rates decreased with increase of water content. For the latter two slow steps of p - toluic acid and 4 - carboxy -benzaldehyde, the rates reach a maximum at a certain water content. There was an optimum water content for the reaction system. The mechanism was interpreted by the competition between coordination effect, which had negative influence on the transfer rate of the electron,and the decrease of the redox potential of the cobalt ion, which had positive influence on the reaction rate.